My recently departed '70 LS5 SS came from GM Atlanta with exactly that combination - 365(+) stock horsepower, with a 400 behind it. If your intent is to drive the car, don't put a shift kit in the trans - it will absolutely break your neck on 1-2 shifts at any rpm range. The 454's have an unbelievable amount of torque. Mine ran 10.5:1 compression, L78 square port heads, Comp Cams stick, header and a Holley 850 DP, Edelbrock single plane, Pertronix, and would do a 360 and melt the tires any time you wanted to. Never a bit of problem from the trans, at all. Bulletproof.
It got traded out for a '68 Z - go figure.